Treatment of motor fuel



No Drawing. Application April Serial No. 723,179

2 Claims.

This invention relates more particularly to the treatment of motor fuels of inferior knock rating such as gasolines produced in the primary nondestructive distillation of paraifinic and some mixed base crudes, although it may also be applied to analogous low boiling cracked products.

More specifically the invention is concerned with a process whereby the hydrocarbons responsible for the knocking tendencies of the fuel are converted into compounds of a more cyclic character by condensation reactions with aromatic hydrocarbons, and in this sense the process may be looked upon as one of arylation.

Owing to the demands made by present day high compression automobile engines, petroleum refiners are confronted with the problem of increasing the anti-knock value of their straight run gasoline fractions which are seldom suitable for use unless they are blended with high antiknock fuels such as,forexample,gasoline produced by intensive cracking operations upon heavy fractions of petroleum or low boiling aromatic fractions from coal and other tars. As an alternative to blending operations, cracking or reforming maybe resorted to, but this is frequently an expensive procedure involving the use of equipment built to withstand temperatures of 950 F., or over and pressures in the neighborhood of 500 pounds per square inch. In addition, the losses are excessive, frequently running as high as 25% when a paraflinic gasoline is brought up to an octane number of approximately 65 to '70.

A further alternative for'increasing the knock rating of straight run gasolines consists in'the use of small quantities of chemical compounds currently known as dopes. These compounds are generally costly and the operation of blending them in the proper quantities with gasoline involves special equipment so that this method. of procedure has its own particular disadvantages.

, The hydrocarbons responsible for the poor knocking tendencies of gasolines are evidently the straight chain parafiins as shown by researches with' pure compounds of this character. The isoparaffins having a-more compact structure have a much higher knock rating than the normal compounds. In the case of olefins the compounds having higher knock ratings are those in which the doublebond is nearest the center of the molecule. The 3 rule regarding the compactness of structure applies to unsaturated chain compounds as well asparaflins.

In the case of simple cyclic hydrocarbons the aromatics have better knock rating than the V naphthen'es, and both groups increase in antiknock value up to some maximum as the ring hydroge'ns are substituted by aliphatic radicals.

' Thus toluol and ethyl benzol have considerably g 2,096,813; UNITED STATES-(PATENT VOFFICE'N TREATMENT OF MOTOR FUEL Vasili Komarewsky, Chicago, 111., assignor to Universal Oil Products Company, Chicago, 111., a corporation of Delaware relationships between hydrocarbon structure and anti-knock value is given to indicate the reasons for the increase of anti-knock value observed in gasolines when treated by the present process, al-

though the entire range of the reactions involvedin different cases is not known and cannot be followed owing to the complex character of the starting materialsand the products formed.

In one specific embodiment the present invention comprises the treatment of gasolines of inferior knock rating, particularly straight run gasoline, with cyclic hydrocarbons in thepresence 4 of aluminum chloride and hydrogen chloride.

It is a feature of the present process that reactions are brought about at temperatures and pressures where aluminum chloride has substantially no effect upon straight run gasolines in the absence of aromatic hydrocarbons. As will be disclosed in later examples, temperatures of from 100 to 150 'C., are suitable and it is hardly ever necessary to exceed the last named temperature. The pressures developed in the course of the reactions will depend upon numerous factors such as the temperature, the character of the particular gasoline undergoing treatment, the ratio of gasoline to aromatic, the percentage of aluminum chloride used and the intimacy of contact obtained, etc. In any event the pressures are not excessive and will seldom exceed 400 pounds persquare inch. It is preferable to use relatively long times of .contact rather than increased temperatures since the former tend to further the desired reactions of condensation between the gasoline and aromatics and lessen the tendency to decomposition with attendant high gas losses and the depreciation of the aluminum chloride due to the formation of hydrocarbon additioncomplexes of varying stability.

In carrying out the operations of the process best results are obtained when employing the socalled batch operation. Thus suitably proportioned mixtures-of gasoline and aromatics such as benzol, toluol; xylols and even semi-refined low boiling coal and-other tar distillates are heated in pressure vessels in the presence of dry anhydrous aluminum chloride and hydochloric acid gas for periods .of from approximately 5 to 20 hours. In order to insure efiective contact bebe circulatedby outside pumps through tubular elements and back to the main supply of liquid,

' the heat necessary for maintaining the required temperature being supplied to' the tubular 'ele-' ment, in accordance with well known procedure in oil cracking and distilling operationa; As the reactions progress a certain amount ot'flxed gases will be produced and thesemay be releaiedautomatically at some predetermined pressure in order to maintain operating conditions constant. Under normal conditions there will'be substantially no-vaporization of gasoline boiling range constituents, though if this occurs the evolved vapors and gases may be passed through condensers and the low boiling gasoline fractions recovered and reserved for future blending.

Following the completion of the reactions the hydrocarbon liquid layer above the spent catalyst may be pumped to units designed to distill, fractionate and recover gasoline boiling range constituents. Fractions boiling higher than the end point desired in the finished gasoline may be added to a subsequent treatment if found suitable.

It is a further feature comprised within the scope of the present invention to react selected fractions of low knock rating gasoline with selected aromatic fractions to obtain maximum efficiency in the development of high anti-knock characteristics. The selection of individual fractions and the use of different aromatics or aromatic mixtures tocombine therewith willbe.

determined largely by experiments since it is not possible to predict the combinations which will give the most beneficial results.

The following data embodies the results 01' runs made with particular fractions of straight run gasolines from Pennsylvania and Mid-Continent fields. Two parts by weight of gasoline and one part by weight of benzol were heated in the presence of 10% by weightbf dry aluminum chloride and 0.5% by weight of hydrogen chloride at a temperature of 100 C. for 20 hours. The maximum pressure developed was approximately 500 place with the lighter gasoline fractions. The

octane numbers were run by the so-called motor method, which is a more severe test than the older research method and is usually more severe in rating materials of higher octane number.

During the treatments which gave the results shown above, pressure was maintained at about 500 pounds per square inch and approximately 10% by weight of gas was evolved which contained about of isobutane. The remaining 5% loss was due to the formation of high boiling addition compounds between aluminum chloride and heavy hydrocarbons probably of a polymerized character.

The preceding specification and the data showing the results obtainedby the use of the present invention show its character and value over present practice but they are for illustrative purposes only and are not to be construed as imposing undue limitations upon its broad scope.

I claim as my invention:

l. A process for improving a straight run petroleum fraction boiling within the gasoline range, which comprises adding to said fraction an aromatic hydrocarbon boiling within the gasoline range and reacting the aromatic with a portion of the petroleum fraction to arylate low antiknock constituents of the latter and form therein condensation products of increased anti-knock value boiling within the gasoline range.

2. A process for improving a straight run petroleum fraction boiling within" the gasoline range, which comprises adding to said fraction an aromatic hydrocarbon boiling within the gasoline range and reacting the aromatic, in the prespounds.

Boiling of B iling 0 t N 0 t No gaso ne- 0 c o. c ggi benzene point oi oi the oi the Kind of gasoline mixture mixture mixture mixture before after the before after the reaction reaction reaction reaction 0.

Pennsylvania str. run.-- -100 75-100 35-106 66 75 Pennsylvania str. run-.. -125 80-125 35 60 67 Rennsyl ania atr. run--- -150 80-150 35-11) 61 57' Mid-Con inent str. run- 75-100 75-100 36-110 67 76 Mld-Continent str. run.-..- 100-126 80-125 32-210 61 09 Mid-Continent str. run----- 125-150 W 86-196 l0 67 It is to be observed that the boiling range 01' the primary gasoline-aromatic mixtures was extended in all cases as a result of the treatment although not outside of the gasoline boiling range.

ence of aluminum chloride and hydrogen chloride, with a portion of the petroleum fraction to arylate low anti-knock constituents of the-latter and form therein condensation products of increased .anti-knock value boiling within the gasoline range.

VASILI KOMAREWSKY. 

